Wireless transmission systems may use transmit diversity, whereby signals are transmitted to a receiver using a plurality of transmit antennas. Some transmit diversity systems may be based on the uplink power control (power control bits, reverse power control) provided by the base stations over the downlink to the mobile terminals. A transmitting modifying communication device may have multiple antenna elements that transmit signals to communicate information. A receiving feedback communication device may receive and extract information from the transmitted signals. Multiple antenna elements for transmission may enhance spectral efficiency and capacity, allowing for more users to be simultaneously served over a given frequency band, while reducing signal degradation caused by multi-path and fading. Transmit diversity parameters may be applied to signals transmitted from two or more antennas, and may modify an effective power distribution detected by receivers, such as base stations.
The transmitted signals may propagate along different paths and may reach the receiving communication device with different phases that may destructively interfere. The received signal quality may change at a receiver that may be attempting to detect a transmission from a mobile terminal, as well as a noise level created by a wireless terminal transmission in base stations attempting to detect signals from other wireless terminals. A signal-to-noise ratio perceived by base stations may change with varying parameters of transmit diversity control. There is a need for a system, method, and apparatus to improve the signal-to-noise ratio.
US Patent Publication No. 2003/0002594, entitled “Communication device with smart antenna using a quality-indication signal” and published Jan. 2, 2003, assigned to the assignee of the present application, the contents of which are hereby incorporated herein by reference, describes using a power control signal, for example, as provided by the power control bit of the CDMA protocol, as a quality indication signal. Information from a power control signal may be used to determine an adjustment of phase difference between the transmitting antennas.